Catalytic cracking and improved catalyst therefor



United States. Patent (1).

No-Di'awing. Application:January:24,=1957 Serial. .'No. :635,952 .1

7 Claims. (Cl."208.--119) This invention relates to the catalytic crackingof -hydro'carbon oils,'- to new and improved catalysts l therefor, and to the preparation of such catalysts.

An object ofthe inventionis to improve the catalytic cracking of hydrocarbon oils in-thedirection of produc ing less gas and coke and more gasoline for any givendepth of conversionand" especially at veryhigh conversion levels.

- Ross E. Van Dyke, Orinda, and John Norton.--Wilson,-.

The catalyst used commercially forthecatalytic crackmg of hydrocarbon oils is either a treated clay catalyst-= such asthat sold under the' name Filtrol' or'a synthetic silica-alurnina composite catalyst containing from about 12 to about 25% alumina.

In composites comprisingsilica and-alumina it is knowna stability of the catalyst increase somewhat as the conthat for-a givenmetho'dof-preparation-the activity-and centrationof alumina-is increased until'a point is reached above-which the selectivity of the catalyst -falls' off In" thelusualmethod of preparation this point is around 15'%-""-Al O For .a number-of years all of the commercial synthetic silica-alumina cracking catalystswontained about 12% A1 0 As" shown; by Ryland et ah, U.S. Reissue- 23,438; the--= alumina, when properly;incorporated,' 'does-not'exise as-w such in the catalyst but is --reacted "with' the silica; the presence of free alumina is undesirable; The amount of'a'lumina that can be'properly combinedwith thesilica depends very much upon'the exact method of-preparation; or,-in other words, on thereactivity of the silica. By preparing the catalyst bythe mannerdescribed-in said Uisp Patent -No.-Reissne 23,438 it is possible--to -properly incorporate up to about 30% alumina thereby producing a the gasoline yield without decreasing the coke and gas,

others that deereaseithecoke-and gas made withoutincreasing the gasoline yield, landstill others that show both advantages.

ltwas thought that low surface catalysts of improved selectivity'might' be prepared by first preparing hydroussilica gel under conditions known to produce stable low surface silica gel-{and incorporating alumina in such by drous' silica gel by hydrolysis of an'aluminum salt. Silica gels of low surface (320 m3/ g.) and remarkable stabil 'ity were prepared by adding ammonium hydroxide to deionized silica sols to'-pH 9.7 and then adding ammoniumfchloride'to gel the silica. Silica-alumina crack- 1 ing catalysts werepreparedfrom-these hydrous silica gels by hydrolyzing aluminum sulfate inthe presence of the silica: hydrogels prepared in'this manner. The resulting catalyst however had substantially higher surfaces and 1 poorer stability.

Further-investigation into the cause of this unexpected i result' indicated that the aggregation of silica particles athi'gh pH in the presence of added salt takes place by reactions: which are-* irreversible The mechanism is believed to be a trueche'mical reaction of Si--OH groups to-form-Si -O Si"linkages-a reaction-which cannot be reversed-by subsequent addition of acid or metal ions such as aluminumions. The irreversible'reaction prob ably occurs-at high pH not only in the case of bonds involving the aggregation-of the sol particles but also in At lower pH values the the sol particles themselves: aggregation of the silica also proceeds by a reversible mechanism. Thefailure to produce the expected catalyst bythe aboveprocedure-isexplainedby-the fact that an insufiic'ient number-of Si O4-Si linkages were formed upon aggregation of the silica particles. Then upon reaction of aluminum ions the a silica particles could not coalesce on drying to form the lower surface gel which was-observedwith the silica itself.

These phenomena areof-great significance relative tothe problem of preparing improved silica-alumina cracking-catalyst; f It is 'clear'that .anessential and important step is in the silica hydrogelpreparation itself. The silica must be aggregated toa considerable degree by the chemical reactiodof SP-QH" groups to form SiO-Si bonds in the hydrogel statewhich cannot be reversed'by sub-' 7 sequent change of the pH. In'the process of the inven tionthisis effectedby'causing the silica to aggregate in more active and stable catalyst. Such catalyst containinga about 25% alumina is nowwidelyused-in commercial practice.

Since catalytic'cracking is catalyzed: by the solid"-sur-- face of the catalyst it has' in the past been the practice toprovide catalystphaving the highest possible available surface pernnit weight. Thus, an available surface of" the fresh'catalyst upwards of 400 m. g. was-considered necessaryv and ,the' commercial synthetic silica-alumina" composite catalysts 'have availablesurface's of the order of 500-600 HL /g. It is now found that-better-"resultsare obtainedif the fresh catalyst has a relatively low available surface rather than a large'available surfaceyprovided that the selectivityiis not impaired."

Itis an-object:of theinvention to provide a catalyst having a smallsurface generally from about'200 mi /gr;

up to about 400 mF/g. "but high activity per unit'ofsurface wherebythe selectivity is improved. 1 More-important, however, it is an object of the invention to provide a new; catalyst which. when .used in catalytic crackingafiords an appreciable improvement in selectivity through-increase in gasoline and/ ordecrease in the coke andfgas'make';

These are usuaHy considered'as two manifestations 'of-the same. phenomenon. In the catalystof thejnvention, how'- ever;v it is found. that they. are "distinct" and separate.

Tlit'is,'we" have foundcertain forniulations that increase-- the 'presence of certain added-"salts at-certain high pH- values. On-the other--hand-, the more complete the ag; gregation by condensation toform SiO-Si bonds the less is the amount ofalumina which can be reacted i.e.,

efficiently combinedto produce the acidic cracking 6318:.

lys t; For this reason'theaggregation of the silica must be carefully controlled and alumina concentrations above those which canbe efficiently. reactedshould be avoided,

We have foundthat catalysts havingsuperior selectivity can be produced'by the methodhereinafter de scribed. The main trick, in ,thismethod resides in producing the silica in a form which 'isparticularly reactive with alumina during the subsequenthydrolysis of the aluminum salt during the preparation. In outline, the first stepin the preparation of the catalyst isthe aggregation of silica to form a soft gel at a very high pH (10.5-11.5) by additionjof a dilute solution ofa water soluble magnesiumgorcalcium salt to,relatively concentrated solution.e.g'. 615%"Si0g', of "sodium silicate e.g., Philadelphia'fQuartz"Company Eibrand (pH ca.11.5).' In. a

typical "case the 'silic'a' concentrationat this point is ap- I Acid maybe added to adjust the final pHjto the range'of 1().0-10.5 and the material is allowed to age -with'stirrin'g fora 'fewminutes.

The --'aggregation-'of"silica-particles depends upon the Patented -May 1 2, 1 959 balance between the van der Waals attractive forces which become rather large at high silica concentration and the strong repulsion of the electrical double layer. The double layer is negatively charged and exhibits a large potential in solutions of high pH. In solution of low pH the double layer is positively charged and the repulsive potential is relatively much weaker. As the pH increases above 7.0-8.0 with increasingOH- concentration the repulsive potential of the electrical double layer increases rapidly due to adsorption of OH* by the silica particles or ions or the abstraction of protons from the surface. With mixtures of sodium silicate and acid this results in a decrease in the rate of polymerization despite the higher concentration of SiOH. This is the region of interest in the preparation of silica gels for the improved catalyst. By adsorbing the divalent rnagnesium or calcium cation onto a silicate ion at high concentration the repulsive negative potential is reduced and because of the strong van der Waals attractive forces the particles aggregate. The divalency of the cation permits extensive cross linking of silicate ions to which considerable amounts of sodium ion are still attached thus permitting formation of large silica particles despite the very high pH of the system. The fact that relatively large particles are formed is reflected by the quite low surface areas of the resulting catalysts. As a result of the reduction in the repulsive negative potential of the double layer, silicate ions in the gel structure are sufficiently close to each otherthat SiOH condensations occur which firmly fix the structure initially induced by the cross linking of the O- Mg-O groups. The silica structure so obtained is considerably different from that obtained when an equivalent amount of acid is added to the silicate solution with conditions otherwise equivalent. That this is the case has been shown by the marked difference in the manner in which aluminum sulfate solution interacts during hydrolysis with the two types of sols or gels.

Following the short period of aging at pH 10.0-10.5 aluminum sulfate solution e.g., 0.4 M is added until the pH reaches a value of about 9.5. At this point ammonium hydroxide e.g., 6 M, is added simultaneously with aluminum sulfate solution to prevent the pH from dropping below 9.0 and preferably to maintain the pH at 9.5.

In some cases a salt, e.g., sodium sulfate, is added to the sodium silicate solution prior to the aggregation step with magnesium or calcium ions. The principal effect of this procedure is to decrease the bulk density or increase the pore volume of the catalyst.

The starting material for the preparation of the improved catalyst is sodium silicate. Potassium silicate can be used but is considerably more costly. The ratio of SiO to Na in the sodium silicate may vary from about 121 up to about 4:1 but is normally between 3:1 and 4: 1.

The sodium silicate is first diluted with water to a silica concentration between about 6% and about 15% by weight or to such an extent that the silica concentration just prior to incorporating the alumina. is between about 3% and 9%, e.g., The pH of the diluted sodium silicate is normally about 11.5. As will be pointed out later, an ammonium salt or an alkali metal salt may be advantageously added to the silicate solution but this is not essential in all cases.

There is then added to the sodium silicate solution with stirring a dilute solution of a soluble salt of magnesium and/or calcium such, for example, as magnesium chloride, magnesium sulfate, calcium chloride, calcium nitrate, calcium acetate or a solution of one of these salts into which is dissolved some magnesium or calcium hydroxide. It is essential that the magnesium and/or calcium salt solution be added to the silicate solution or that the two solutions be added simultaneously to a mixing vessel. It is essential that the solution of the magnesium and/ or calcium salt be quite dilute, preferably between 0.05 and 0.5 molar and that the pH of the silicate solution during the addition of the magnesium and/or calcium salt be maintained at a high value e.g. about 10.5 or above. The amount of magnesium and/ or calcium should be in the range of to mol per mol of SiO It should be noted that when the magnesium and/or calcium salt is added tothe sodium siliciate solution its effect on the pH is essentially the same as the addition of an equivalent molar quantity of sulfuric acid. The maximum amount of magnesium and/ or calcium salt specified is, however, insuflicient to reduce the pH below about 10.5,

Under the above conditions the magnesium and/ or calcium is completely reacted in the silica aggregate. The material at this point hasa pH of at least 10.0, normally contains about 5% silica by weight, and is in the form of a very soft gel (resemblingwaffle batter) which is thixotropic but will not set to a firm gel on standing. If the concentration of silica at this point is above about 9% a catalyst of undesirable low bulk density is produced. On

the other hand, if the concentration of silica is below about 3% the bulk density generally is too high. At 5% concentration the bulk density of the catalyst is normally about 0.30 to 0.60 which is the range best suited for fluid catalyst operation.

If the pH at this point is above 10.5 it is preferably brought down to the range of 10.0 to 10.5 which can be effected by adding acid, e.g., sulfuric acid or hydrochloric acid,

In the procedure described above the magnesium and/ or calcium is reacted in the silica aggregate at a very high pH after which the pH is reduced to the range of 10.0 to 10.5 by the addition of acid. In an alternative procedure the same amounts of these reagents are used but the acid is introduced prior to the magnesium and/ or calcium salt solution. In this procedure the magnesium and/ or calcium is reacted at a pH nearer to the value of 110.5. In a further alternative the acid and the magnesium and/ or calcium salt solution may be added simultaneously. In any case, the pH of the bulk solution during the addition of the magnesium and/or calcium salt solution is not allowed to drop below about 10.0 for any appreciable time and preferably not below 10.5.

The creamy material may be stirred for a few minutes, e.g., 15 minutes, to insure equilibrium.

In the preferred procedure a solution of aluminum salt is slowly added with stirring to the creamy silica (pH 10.0 to 10.5) until the pH is reduced to about 9.5. Additional aluminum salt solution and ammonium hydroxide are then added at such a rate as to maintain the pH at this value until all of the alumina to be incorporated has been added.

The pH at which the hydrolysis of the aluminum salt is carried out is quite critical. The preferred value is 9.5. The pH- may, however, vary somewhat, e.g., 0.5 unit, from this value. Higher pHs, e.g. up to 10.5 can be used but at pH above 10.0 the resulting catalyst is found to contain large amounts of bonded sodium which is difficult to remove without affecting the properties of the catalyst. On the other hand, at pHs below 9.0 the mag-- nesium and/ or calcium is largely removed from the catalyst. The catalyst produced by the above procedure not only produces less coke and more gasoline than conventional silica-alumina catalyst but it also produces sig nificantly better yields of valuable C and C olefins. In this procedure most, but not all, of the silica is aggregated prior to incorporating the alumina and the remaining silica is aggregated with the alumina.

The pH of the silica may be brought down to the 9.5 value by the addition of acid prior to incorporating the alumina. The aluminum salt solution is then added along with ammonium hydroxide while maintaining the pH at the stated value as described above. In this case, the silica is essentially all aggregated prior to incorporating the alumina.

The amount of aluminum incorporated in the catalyst may be as as about 35% by weight, calculatedas Alg'O and Based" on the finished eataly'st, butis prefeiablyin the range downward: of 30%, e.g. 12 .40%.- Lesser amounts "dowfi"t""1% can "be; used but when'les'ser amounts "are incorporated it is found that the' catalyst tends'toretain sodiumwhich'is difficult to remove.

The amountsbf magnesium and/orcalcium specified aboveare equivalent to about 1% t0"9%by weighteal culated'asMgO and CaO'ba'sed on the'firiished catalyst. containing about 20%" A150 The improved gasoline yield and reduetion of coke make 'is not strongly dependent "on the concentration of magnesium and/orcalcium'used'in'th'e' ranges specified. Howevento 'obtaingf, in additiom the increased yield of'valuable C3 and-C4 olefins it is essential that at least about 3% MgO and/or Ca O be retained in" the catalyst! As previously s'tated,'"it is advantageous to addan ammoniumsaltor'alka1imetal 'salfieg. the chloride or sul fate; 'tothe sodiunisilicate solution prior'toincorporating' the mag'nesiuhi"and/or calcium; This 'addition is'par ticularly advantageous when thes'odium' silicate used has a lii'gh'ratio of SiO 'to Na O, e.g. above 3. The'salt may be dissolved in' the "sodium' silicate solution in any con-' centration up to' about 0.1 mole per mole of SiO After aggregatin'g'th'e silica and combining the alumitia as' describ'edthe hydrous product is filtered,'washed and dried. It is desirable to wash the catalyst with an am-"L moniumsalt solutioneg. the nitrate; chloride, or'acetat'e; at a high pH; e.g. 9.5, toremove' sodium salts. This may be" done prior to drying the" catalyst or after 'dryingl' The materialmay be'dried'and'then ground or formed into pieces "or the'desired size 'and-sha'pe for fixed'bed'or moving bed operation,or it may be 's'praydried to produce a microspheroidal'powder suitable foi use the fluid-f ized catalyst technique". Prior'to' using" the catalyst it is preferably, but'not'necess'arily, calcined'to reducethe moisture content "down to' a valueof 15% 'or" somewhat below this figure. l

T he catalyst of the invention does not have the adverse electrostatic properties ofthe proprietary silica-magnesia cracking catalyst andconsequently it is easily fluidized.v 40 It 'can,'of course, be used alone 'but'because of its better"- fluidization properties it is particularly suited for use in admixture with natural clay catalyst or 'theconven'tional synthetic silica-alumina catalyst.

The catalyst of the invention is useful for-the 'craekin'g--. of types-of hydrocarbon oilskommonly usedas cat i aly'ticcracking feedstocks'. It is especially advantageous for the catalytic cracking of very'heavy hydrocarbon oils havin'g'molecular weightabo've 300, "and especially when cracking'to higher than usual conversion levels 'e.g. 50 or above'g Conversion is defined as 1 00 minus the per cent'of recovered on boiling ab'oVe450-'F.

The catalytic cracking may becarried out by contacting'the' vapors of the oil to be cracked in a suitable catalyticcracking' reactor with the catalystat temperatures 5 from about 850 to about 1050" F. and pressure-from about l to 4 atm; abs.

EXAMPLE 1 A quantity" (516 g.) of sodium silicate of the ratio 3.2 SiO /Na O and containing 29.1% SiO Was'dil'uted to 2.5 liters. A solution of magnesium sulfate was prepared by dissolving'81.9 g. MgSO -7H O in 500 ml. water. This 0.664 M solution was equal to 0.13 mole Mg'lr'nole SiO This magnesium sulfate'solutio'n-was added to the sodium silicate solution with stirring over'a period of about 20 'minutesat approximately room temperature. The pH'of the resulting slurry'was reduced to 10.45'by v the addition of 32 ml. of 6.1 N H SO -and the slurry" was stirred" for 45 minutes. Thematerial at'this stage was a soft gel of approximately the consistency of wafiie batter.

A 1.02"M solution of aluminum sulfate was prepared and0.361 liter of this solution was diluted to 0.92 liter.- The pH of-the gel was then reduced to 9.5 byyaddition of this "dilute" aluminum sulfate solution which required 1 6 0.2}7 6 literw At 'this point the addition of 6 M ammoniumw. hydroxide was be'gun sirnultan'eously withthe remainder oftheY' aluminum-sulfate solution at a rate-to maintain... the pI-I 5:9.4 915. The resulting silica-alumina-magnesia: composite"was -'filte'redfrom the mother-liquor, washed Withvvater; furtherwashed with 0.2 M ammonium nitrate solution. atpH. 9.5; furth'er washed with water-and then dried andcalcined 4hours at- 565 C. 'The resulting cat-. i alystcontained 6% 'MgO, 19% A150 the balance being i silica. The available surface area was'308 na /grand the pore volume was 0.56 (Sc/gm.

' EXAMPLE 2 A quantity :of :sodiuiiisilicate' (516' g. .having' the ratio 3.2 SiOE/Na' O and'containing 29.1% SiO was diluted' j to 2.5 liters. A 0.541. M solution of calciunt'chloride" was preparedby'fdissolving'30g; anhydrous CaCl in 500 ml." water." This"calcium chloridesolution containing f 0.11 mole Ca per mole SiO was added over-a p'eriojdof 20 minutes stirring'to the diluted sodium silicate solutionQ 'The'pI I of the resulting slurry'was then 'reduced' to by thefaddition"of46 of 6.1 N H 80 This f slurry was stirred for 45 minutes at essentially room temperature'f A"0.4 M "aluminum sulfate solution (0.92"" liter)" containng"0.l6 mole A1 0 permole SiO was pre? paredf The'pH of the slurry was reduced to 9.5 by the addition of part'ofthis' aluminum sulfate solution, the amount required bein'g0.29 liter. Ammonium hydroxide solution (6 'M) "was then added simultaneously with the remainderof'the alun'iinurn sulfate solution at a' rate to maintain 'the'pI-I at 9.4-9.5. The resulting gel was filtered; washed ith water; washed with 0.2M ammonium nitrate at pH "9.5', gain washed with water, dried and'calcin'em at 565 C. for- 4 hours; 1

The'resulting catalyst contained. 4.3%Q'Ca0, 19% A150 thebal ance being SiO Its available surface area: was 277m.' /g;'and'its' pore volume'was 0.78 cc/g. The." disere'pancybetweerithe amount of calcium'used in'the'lpreparation andthe amount of calcium-in the finished catalyst is dueto'the'removal of part of the calcium by solution during the time thatthe medium was at a pH of 9.5.

EXAMPLE 3 A 'quantity(5:l6 g)" of "stadium 'silcate having 'the' ratio 3.2 SiO;/Na O and containng'129.l% 'SiOg wasdiluted'to 1.5 liters with'waten' To this solution therewas addedffml. of'a 1 M'solution o'f'Na SO4. A dilute (0.2026 M)--'so1ution offmagnesium sulfate was preparedin-an amount'('1.'5 liters) equal'to 0.12 mo'le/moleSiOg; This magnesium sulfate solution was added tothesolution of silcateand sodium sulfate with*sti rring at essentially -t room temperature over' a period of 20 minutes; The stirring was then continued for a further l0'minutes to ensurecompletion of-the reaction? The pH of the mixturewas then-reduced-to 10.5 through'the addition of 22'm1. of- 6.l-N H 804. 1 Aso'lutionofaluminum sulfate was pre-" pared -in an amount-equal to 0.16mole/mole SiO or 0.995 literof 0.4 M'aluminum sulfate. The pH of the mix-1:" ture was then reduced to 9.5 by the addition of part of.

0 thisaluminums'ulfate solutiom -the amount required EXAMPLE 4 I A quantity of sodiumsilicate- (1100 g. havingsthe ratio 3 3 .2" SiQfl-NagO; andcontaining 27.3 SiO was dis;

luted with water to 2.4 liters. A quantity (292 m1.) of

l M magnesium sulfate was diluted to 3.6 liters. This. diluted magnesium sulfate solution was added to the diluted sodium silicate solution with stirring at essentially room temperature over a period of 45 minutes. The pH of the resulting slurry was then reduced to about 10.5 through the addition of 196 ml. of 6.1 N H 80 and the slurry was allowed to age at this pH for one hour. The pH of the slurry was then reduced to 9.5 by the addition with stirring of 70 ml. of 0.97 M aluminum sulfate solution. Ammonium hydroxide was then added simultaneously with a further quantity (533 ml.) of the 0.97 M aluminum sulfate solution at a rate to'maintain the pH at 9.359.5. The resulting gell was filtered, washed with water,rwashed with 0.5 M ammonium nitrate at pH 0.5, further washed with water, dried and calcined at 565 C. for 4 hours.

The resulting catalyst contained 2.2% MgO and 17% A1 the balance being SiO Its available surface area was 310 m. /g.

The above catalysts were each steamed under 1 atm. steam pressure for 20 hours at 576 C., in order to simulate a short period of use under practical operating conditions, and they were then used for the catalytic cracking of a commercial West Texas flashed distillate having a molecular weight of 319 at 500 C., 1 atm. pressure and a 60 minute process period. A pretreatment such as that here given is considered desirable before testing a cracking catalyst since it is found that the properties of all fresh cracking catalysts are drastically altered even during the first few hours of commercial use and the behavior of the freshly prepared and nonpretreated catalyst bears little relation to its behavior in commercial application.

The results are shown in the following Table 1.

Table 1 Catalyst Ex. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4

WHSV 2. 35 1.61 2. 32 1. 62 2. 33 Percent Reacted 53.6 60.2 62. 6 60.9 56.9

0 4-04 olefins. 9. 3 11.3 10. 0 11. 10. 4 coke 1.40 2. 36 1. 35 2. 81 2. 19

Relative gasoline 106 107 102 105 103 Relative 0 -1-04 olefin 95 105 105 106 100 Relative coke 65 67 68 76 80 Relative activity 112 115 106 104 105 The figures of primary interest are the relative yields and activities shown in the lower part of the above table. These figures show the yields of gasoline, C +C olefins and coke obtained with these catalysts relative to the corresponding yields of these products obtained with the standard catalyst at the same conversion level, the standard catalyst being in each case assigned a yield rating of 100. The relative activities are on a liquid hourly space velocity basis and indicate the relative amount of cracking catalyzed by a unit of catalyst surface, the standard catalyst being assigned a rating of 100.

It will be noted that in all cases the amount of coke produced was only 65 to 80% of that produced by the standard catalyst at the same conversion level. The amount of gasoline produced was, on the other hand, in all cases significantly higher. The amount of valuable C and C olefins was in general significantly higher, especially at the higher conversion levels.

The importance of these improved results which are clearly outside of experimental error will be appreciated when it is considered that in this field it takes a very little percentage improvement to afford a large monetary gain. For example, for a major oil company having a catalytic cracking capacity of 200,000 b./d. and using 50 tons a day of fresh cracking catalyst costing $300/ton, an increase in the value of the catalytic cracking products by as little as one cent per barrel of feed represents an improvement worth $2,000 per day, and a decrease in the cost and/or amount of catalyst by 10% represents a saving of $1,500 per day. With the catalyst of Example 1 and at equal conversion calculations indicate an increase in product value of about 10/bbl. of cracker feed, and on the basis of equal coke production (conversions differing) the indicated increase in product value is about 17/bbl. of cracker feed.

In addition to the improvements afforded in the cat alytic cracking process itself it should be noted that the catalyst preparation method allows the use of relatively concentrated solutions of sodium silicate and very substantially reduces the consumption of the sulfuric acid.

We claim as our invention:

1. In the process for the catalytic cracking of a hydrocarbon oil to produce catalytically cracked gasoline and C and C olefins the improvement which comprises contacting the hydrocarbon oil to be cracked in the vapor phase at a temperature between 850 F. and 1050 F. and a pressure from 1 to 4 atmosphere absolute With a solid catalyst prepared by reacting at a pH maintained at a value of at least 10.0 with a sodium silicate solution containing between about 6% and 15% of SiO a dilute solution of a water soluble salt of a metal selected from the group consisting of magnesium, calcium, and mixture thereof, said dilute solution being from about 0.05 to 0.5 molar and being in an amount to supply from about to 1% mole of the metal salt per mole of SiO bringing the pH of the reaction mixture to a value in the range of 10.0 to 10.5, then adding to said reaction mixture 2. solution of a water soluble salt of aluminum in an amount to incorporate between 12 and 30% A1 0 based on the calcined catalyst and adding ammonium hydroxide during the addition of said aluminum salt solution at a rate adjusted to prevent the pH of the reaction mixture from dropping below 9.0, then filtering, Washing and calcining the resulting hydrogel.

2. In the process for the catalytic cracking of a hydrocarbon oil to produce catalytically cracked gasoline and 1 C and C olefins the improvement which comprises contacting the hydrocarbon oil to be cracked in the vapor phase at a temperature between 850 F. and 1050 F. and a pressure from 1 to 4 atmospheres absolute with a solid catalyst prepared by reacting at a pH maintained at a value of at least 10.5 with a sodium silicate solution having a mole ratio of SiO to Na O between about 3 and 4 and containing between about 6% and 15% of SiO a dilute solution of a water soluble salt of a metal selected from the group consisting of magnesium, calcium, and mixture thereof, said dilute solution being from about 0.05 to 0.5 molar and being in an amount to supply from about to /s mole of the metal salt per mole of SiO the reaction mixture at this point being a creamy gel containing about 5% SiO then reducing the pH of the reaction mixture to a value in the range of 10.0 to 10.5, then adding to said reaction mixture a solution of a Water soluble salt of aluminum in an amount to incorporate between 12 and 30% A1 0 based on the calcined catalyst and adding ammonium hydroxide during the addition of said aluminum salt solution at a rate adjusted to maintain the pH of the reaction mixture at 9.5:05, then filtering, Washing and calcining the resulting hydrogel.

3. In the process for the catalytic cracking of a hydrocarbon oil to produce catalytically cracked gasoline and C and C olefins the improvement which comprises contacting the hydrocarbon oil to be reacted in a vapor phase at a temperature between 850 F. and 1050 F. at a pressure of 1 to 4 atm. abs. with a solid catalyst prepared by preparing a solution of sodium silicate having a concentration of Si between about 6% and 15 adding to said sodium silicate solution a positive amount less than 0.1 mole/mole of SiO of a salt selected from the group consisting of the water soluble salts of sodium and ammonium; reacting with the resulting mixture While maintaining the pH at a value of at least 10.5 a dilute solution of a water soluble salt of a metal selected from the group consisting of magnesium, calicum, and mixtures thereof, said dilute solution being from 0.05 to 0.5 molar and being in an amount to supply from about to mole of the metal salt per mole of SiO in the sodium silicate solution; after combining the said solutions bringing the pH of the resulting liquid to a value within the range of about 10.0 to 10.5; then adding to said liquid a solution of a water soluble salt of aluminum in an amount to incorporate about 20% A1 0 based on the calcined catalyst, and adding ammonium hydroxide during the last said addition at a rate adjusted to maintain the pH of the liquid at 9.5:05; filtering the resultant hydrogel from the liquid and washing, drying and calcining the same.

4. Process for the production of a catalyst having pronounced activity for the cracking of hydrocarbon oils with low formation of coke which comprises preparing a solution of sodium silicate having a concentration of SiO between about 6% and 15%, reacting with said sodium silicate solution while maintaining the pH at a value of at least 10.0 a dilute solution of a water soluble salt of a metal selected from the group consisting of magnesium, calcium, and mixtures thereof, said dilute solution being from about 0.05 to 0.5 molar and being in an amount to supply from about to /5 mole of the metal salt per mole of SiO in the sodium silicate solution; after combining the said solutions bringing the pH of the resulting liquid to a value within the range of about 10.0 to 10.5; then adding to said liquid a solution of a water soluble salt of aluminum in an amount to incorporate between 12 and 30% A1 0 based on the calcined catalyst, and adding ammonium hydroxide during the last said addition at a rate adjusted to prevent the pH of the liquid from dropping below 9.0; filtering the resultant hydrogel from the liquid and washing, drying and calcining the same.

5. Process for the production of a catalyst having pronounced activity for the cracking of hydrocarbon oils with low formation of coke which comprises preparing a solution of sodium silicate having a concentration of SiO between about 6% and 15%, reacting with said sodium silicate solution while maintaining the pH at a value of at least 10.5 a dilute solution of a water soluble salt of a metal selected from the group consisting of magnesium, calcium, and mixtures thereof, said dilute solution being from about 0.05 to 0.5 molar and being in an amount to supply from about to /s mole of the metal salt per mole of SiO;, in the sodium silicate solution; after combining the said solutions bringing the pH of the resulting liquid to a value within the range of about 10.0 to 10.5, the reaction mixture at this point being a creamy gel containing about 5% SiO then adding to said liquid a solution of a water soluble salt of aluminum in an amount to incorporate about 20% A1 0 based on the calcined catalyst, andadding ammonium hydroxide during the last said addition at a rate adjusted to maintain the pH of the liquid at :05; filtering the resultant hydrogel from the liquid and washing and calcining the same.

6. A catalyst having pronounced activity for the cracking of hydrocarbon oils with low coke formation prepared by adding at a pH maintained at a value of at least 10.5 to a sodium silicate solution containing between about 6% and 15% of SiO a dilute solution of a water soluble salt of a metal selected from the group consisting of magnesium, calcium, and mixture thereof, said dilute solution being from about 0.05 to 0.5 molar and being in an amount to supply from about ,6 to /5 mole of the metal salt per mole of SiO bringing the pH of the mixture to a value in the range of 10.0 to 10.5, then adding to said mixture a solution of a water soluble salt of aluminum in an amount to incorporate between 12 and 30% A1 0 based on the calcined catalyst and adding ammonium hydroxide during the addition of said aluminum salt solution at a rate adjusted to prevent the pH of the reaction mixture from dropping below 9.0, then filtering, washing and calcining the resulting hydrogel, said catalyst being further characterized by having an available surface below 400 m. /g. and a bulk density between about 0.30 and 0.60 g./cc.

7. A catalyst having pronounced activity for the cracking of hydrocarbon oils with low coke formation prepared by reacting at a pH maintained at a value of at least 10.5 with a sodium silicate solution containing between about 6% and 15% of SiO a dilute solution of a water soluble salt of a metal selected from the group consisting of magnesium, calcium, and mixture thereof, said dilute solution being from about 0.5 to 0.5 molar and being in an amount to supply from about to /5 mole of the metal salt per mole of SiO then reducing the pH of the reaction mixture to a value in the range of 10.0 to 10.5, the reaction mixture at this point being a creamy gel containing about 5% SiO then adding to said reaction mixture a solution of a water soluble salt of aluminum in an amount to incorporate between 12 and 30% A1 0 based on the calcined catalyst and adding ammonium hydroxide during the addition of said aluminum salt solution at a rate adjusted to maintain the pH of the reaction mixture at 9.5:05, then filtering, washing and calcining the resulting hydrogel, said catalyst being further characterized by having an available surface below 400 m.'-/g. and a bulk density between about 0.30 and 0.60 g./cc.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN THE PROCESS FOR THE CATALYSTIC CRACKING OF A HYDROCARBON OIL TO PRODUCE CATALYTICALLY CRACKED GASOLINE AND C3 AND C4 OLEFINS THE IMPROVEMENT WHICH COMPRISES CONTACTING THE HYDROCARBON OIL TO BE CRACKED IN THE VAPOR PHASE AT A TEMPERATURE BETWEEN 850* F. AND 1050* F. AND A PRESSURE FROM 1 TO 4 ATMOSPHERE ABSOLUTE WITH A SOLID CATALYST PREPARED BY REACTING AT A PH MAINTAINED AT A VALUE OF AT LEAST 10.0 WITH A SODIUM SILICATE SOLUTION CONTAINING BETWEEN ABOUT 6% AND 15% OF SIO2, A DILUTE SOLUTION OF A WATER SOLUBLE SALT OF A METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, CALCIUM, AND MIXTURE THEREOF, SAID DILUTE SOLUTION BEING FROM ABOUT 0.05 TO 0.5 MOLAR AND BEING IN AN AMOUNT TO SUPPLY FROM ABOUT 1/50 TO 1/5 MOLE OF THE METAL SALT PER MOLE OF SIO2'' BRINGING THE PH OF THE REACTION MIXTURE TO A VALUE IN THE RANGE OF 10.0 TO 10.5, THEN ADDING TO SAID REACTION MIXTURE A SOLUTION OF A WATER SOLUBLE SALT OF ALUMINUM IN AN AMOUNT TO INCORPORATE BETWEEN 12 AND 30% AL203 BASED ON THE CALCINED CATALYST AND ADDING AMMONIUM HYDROXIDE DURING THE ADDITION OF SAID ALUMINUM SALT SOLUTION AT A RATE ADJUSTED TO PREVENT THE PH OF THE REACTION MIXTURE FROM DROPPING BELOW 9.0, THEN FILTERING, WASHING AND CALCINING THE RESULTING HYDROGEL. 